Heterojunction MXene@PANI Inks with Fast Ion Migration and Strong Structural Stability by Microcosmically Intercalating and Macroscopically Cross-Linking for Flexible Microsupercapacitors

Two-dimensional transition metal carbide/nitride (MXene) conductive inks have broad application prospects in the scalable production of flexible, printable electronics. However, its intrinsic self-stacking and structural instability badly hinder the practical application of MXene inks for microsupercapacitors. Here, we demonstrated quickly ion-transporting and structurally stable heterojunction Ti₃C₂T_<i>x</i>/polyaniline inks by microcosmically intercalating and macroscopically cross-linking for microsupercapacitors. Theoretically, its lower migration energy barrier (2.44 eV) than that of pure Ti₃C₂T_<i>x</i> (3.29 eV) can naturally provide faster ion transport ability. Moreover, its stronger density of states near the Fermi level and the charge redistribution at the heterojunction interface can intrinsically promote easier electronic transmission during electrochemical processes. Experimentally, the as-prepared microsupercapacitors display a high areal capacitance of 71 mF cm^-2, excellent rate performance (93.6%), and long cyclic stability (retains 95.2% of initial capacitance after 10,000 cycles), much more than those of pure MXene microsupercapacitors (42.7 mF cm^-2, 72.5% and 84.3% retention). Evidently, this work provides a way for MXene-based heterojunction construction, promoting practical applications of high-performance MXene electronic inks.